Prevention of mother-to-child transmission

Derek Thaczuk

A woman on antiretroviral (ARV) therapy before becoming pregnant should be able to continue treatment throughout the pregnancy, although the particular drugs in the regimen or dosing might be changed. If not on ARV therapy, immune status needs to be monitored throughout the pregnancy. The use of ARVs should be considered at some point to reduce the risk of transmission. 

Transmission can occur at any time during pregnancy, labour, or after delivery through breastfeeding. Several factors are associated with a higher risk of transmission, including the maternal viral load and CD4 cell count.

In the absence of any intervention, an HIV-positive woman has a 15 to 30% chance of transmitting the virus to her baby during pregnancy and delivery. If she breastfeeds, there is an increased 5 to 20% risk of transmission. With ARV treatment, the risk of vertical transmission can be reduced to under 2%. 

In the developed world, widespread use of antiretroviral therapy during pregnancy has been associated with a dramatically reduced incidence of mother-to-child transmission (MTCT) among women with HIV who do not breastfeed. Similar success is seen in under-resourced areas when prenatal care and access to antiretrovirals is provided.

There is little evidence to date that antiretroviral drugs cause a significant risk of serious abnormalities; however, the long-term safety of exposure to antiretroviral drugs in the womb and early in life is not known. The US guidelines point out that risk depends not just on the drug itself, but the dose of the drug used, the gestational age of the foetus at exposure, duration of exposure, interaction with other agents, and perhaps, the effect of the mother and foetus's genetic make-up.1

The management of any pregnancy in an HIV-positive woman requires careful consideration of the balance between the mother's health needs, locally available treatment options, the need to reduce transmission, and the adverse effects of antiretroviral therapy. Recommended treatment options vary by country and local resources.

Most women in the developed world choose to feed their child with infant formula. However, in resource-limited settings, replacement feeding is not always a viable option because of the lack of safe water, a reliable supply of infant formula, or social norms.

In areas where malnutrition and childhood illness are common, infants who are not breastfed are more likely to die from other causes, such as bacterial infections. Making the choice not to breastfeed can also lead to stigmatisation, as not doing so can lead to speculation about the mother's health status.

Early weaning was a strategy explored to lessen the risk of MTCT, but it does not improve HIV-free survival time, morbidity or mortality for the infant.

In prevention of mother-to-child transmission (PMTCT), some of the issues being studied are:

  • The effect, if any, of antiretrovirals on the rate of low birth weight and preterm labour.
  • The viral dynamics of HIV in breast milk.
  • The use of ARVs, by the mother or infant, to lower the risk of transmission while breastfeeding.
  • Whether there is a heightened incidence of proinflammatory response and immune reconstitution syndrome in women after giving birth. 
  • Whether the use of ARVs in general, or particular drugs or drug classes, increases the incidence of birth defects.
  • Strategies for preventing drug resistance.

The guidelines consulted in the preparation of this section are:

  • British HIV Association and Children's HIV Association Guidelines for the management of HIV infection in pregnant women, 2008.2
  • World Health Organization, Guidance on global scale-up of the prevention of mother-to-child transmission of HIV.3 Antiretroviral drugs for treating pregnant women and preventing HIV infection in infants.4
  • US Public Health Service Task Force Recommendations for use of antiretroviral drugs in pregnant HIV-infected women for maternal health and interventions to reduce perinatal HIV transmission in the United States.5

References

  1. Perinatal HIV Guidelines Working Group Public Health Service Task Force Recommendations for Use of Antiretroviral Drugs in Pregnant HIV-Infected Women for Maternal Health and Interventions to Reduce Perinatal HIV Transmission in the United States. July 8, 2008 Available online at aidsinfo.nih.gov [Accessed 3 Nov 2008): pp 1-98, 2008
  2. de Ruiter A et al. British HIV Association and Children's HIV Association guidelines for the management of HIV infection in pregnant women 2008. HIV Med 9: 452-502. Available online at www.bhiva.org, 2008
  3. Interagency Task Team on Prevention of HIV Infection in Pregnant Women, Mothers and their Children Guidance on global scale-up of the prevention of mother-to-child transmission of HIV. World Health Organization, Geneva, 2007. Available online at who.int/hiv/pub/guidelines [accessed 3 Nov 2008], 2007
  4. World Health Organization Antiretroviral drugs for treating pregnant women and preventing HIV infection in infants: Recommendations for a public health approach: 2010 version. World Health Organization, Geneva 2010. Available online at http://www.who.int/hiv/pub/mtct/antiretroviral2010/en/index.html. [Accessed November 9, 2010], 2010
  5. Panel on Treatment of HIV-Infected Pregnant Women and Prevention of Perinatal Transmission. Recommendations for Use of Antiretroviral Drugs in Pregnant HIV-1-Infected Women for Maternal Health and Interventions to Reduce Perinatal HIV Transmission in the United States. May 24, 2010; pp 1-117. May 24, 2010; pp 1-117. Available at http://aidsinfo.nih.gov/ContentFiles/PerinatalGL.pdf. [Accessed Nov 13, 2010.], 2010